Final answer:
The electron transport chain releases energy as electrons move through a series of redox reactions, creating an electrochemical gradient by pumping protons across the mitochondrial membrane. Chemiosmosis harnesses this gradient to power ATP synthase, which synthesizes ATP. This coupling of exergonic electron transport to endergonic ATP production is known as oxidative phosphorylation.
Step-by-step explanation:
In general terms, the exergonic "slide" of electrons down the electron transport chain (ETC) is an energy-releasing process. This occurs as electrons are passed from molecules like NADH and FADH2 down a series of carriers that make up the ETC, which is embedded in the inner mitochondrial membrane. As these electrons move to lower energy states, the energy released is used to pump protons (H+) across the membrane, creating an electrochemical gradient. This part of the process is exergonic because it releases free energy.
The endergonic production of ATP by chemiosmosis utilizes the energy from the proton gradient. As protons flow back into the mitochondrial matrix through ATP synthase, an enzyme that works like a turbine, this exergonic flow is coupled with the endergonic phosphorylation of ADP to form ATP. This flow is essential for the ATP synthase to add a phosphate group to ADP, producing ATP in a process known as oxidative phosphorylation. The energy stored in the electrochemical gradient, originating from the exergonic electron transport, drives this endergonic synthesis of ATP.
Therefore, the entire process is a sophisticated coupling mechanism, where the exergonic release of energy from electron transport is directly linked to the endergonic production of ATP—demonstrating a harmonious flow and conservation of energy within cellular respiration.